Luffy being much stronger than Zoro doesn't make Zoro worthless. Zoro is still a beast and can take on other strong characters that the rest of the crew can't. Luffy just has to take on the strongest since he's the strongest, Zoro can get the next guy
Even more with his dream like now I see such happening at EoS unless it has an absurd power jump to catch-up with Mihawk who at worst is = shanks.